Updated October 29:We’re updating this forecast to move South Carolina from Lean R to Toss-up.As this week’s Power Rankings reported, Republicans already viewed this as an uncomfortably close race. That belief is now widely shared.Tonight, the president is headed back there to help Sen. Darline Graham in the Upstate, where she underperformed in her primary runoff against Rep. Ralph Norman.New polling has Democratic challenger Annie Andrews and Graham tied at 48%-48%.The Senate is still a toss-up with six states to decide the majority. On a good night for the Democrats, their ceiling rises to 5...